Automatic Bed Probing vs Automatic Bed Leveling

So I got an error in compiling Marlin:

#error "Disable PREHEAT_BEFORE_LEVELING when using PREHEAT_BEFORE_PROBING."

I have no idea why these two should conflict with each other.
It raises a question for me, what is the exact difference between the two?
I mean they both should compensate for bed surface irregularities so what causes the real difference that they couldn't both run with preheating?
I couldn't find an appropriate explanation in Marlin's documentation for the difference between the two.
I have a very large bed and I'm going to use the BLTOUCH to correct the bed surface height before each print. What option I can make use of?

Edited 1 time(s). Last edit at 09/09/2022 10:03AM by sajjsamm.

As best I can tell , PREHEAT_BEFORE_LEVELING came first.

The only differences that I could see mentioned is PREHEAT_BEFORE_PROBING also preheats before G30 (and probably M48). Hmmmm ... I wonder if it preheats during G28 when USE_PROBE_FOR_Z_HOMING is enabled.

I do see that the DWIN displays make decicions based on if PREHEAT_BEFORE_LEVELING is enabled or not.

So what is the difference between probing and leveling in action?
Which one may I use to create a map of the print surface imbalance to compensate during the print starting with each print and for all layers including first layer?

Any ideas?

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sajjsamm
Any ideas?

I can't answer your specific question, but I use an under bed piezo probe on my delta (https://reprap.org/forum/read.php?424,885697). Every few months I do a delta calibration, followed by a UBL bed leveling with a 1mm fade height. Every few months because the ambient temperature in my shop changes with the seasons, which affects the dimensions of the printer.

I can reliably print a 5 micron thick single layer of PLA over the entire surface of the 380mm diameter textured glass bed.

I'm wondering about the procedure and I'd like to know more about the difference since my bed is going to be huge like 1200mm*600mm and I need to be confident about my bed's surface before printing a huge first layer before it turns out to be a total mess.
I'm going to use BLTOUCH in this case my probe = BLTOUCH.
So using a BLTOUCH to create a map of the bed's surface is gonna be called probing or leveling???
I can do it the hard way but it cost me time and materials.

Quote
sajjsamm
I'm wondering about the procedure and I'd like to know more about the difference since my bed is going to be huge like 1200mm*600mm and I need to be confident about my bed's surface before printing a huge first layer before it turns out to be a total mess.
I'm going to use BLTOUCH in this case my probe = BLTOUCH.
So using a BLTOUCH to create a map of the bed's surface is gonna be called probing or leveling???
I can do it the hard way but it cost me time and materials.

Sounds like semantics to me. I'd say the physical act of using a BLTouch (or any other "distance to bed" sensor) is called probing. Applying the resulting map of bed variation from an ideal plane is called leveling.

I tend to run both delta calibration and UBL multiple times. For instance, running delta calibration the first time will get me into the ball park. I then save that result, reset the printer, and do it all again. Each time the calibration gets tighter and tighter. After about 5 iterations, the standard deviation of an M48 test is 0.000000. My "probe" is the nozzle contacting the bed (https://www.youtube.com/shorts/UJbq8bXZKmc). If the nozzle and bed are not surgically clean, all bets are off. It's sensitive enough to detect a film of finger oil on the bed. A cat hair is like tripping over a log. I believe the best you'll get out of a BLTouch is about 0.002-0.005mm due to the inherent hysteresis in its detection method, which is still darn good.

The same applies to UBL. Run, save, reset, re-run. I stop when the standard deviation is 0.003, which is the 5 micron resolution of my printer kinematics. It can never be zero.

Keep in mind that this is only necessary if I do something mechanically drastic to the printer, or if the ambient temperature changes quite a bit (5C or so). Two or three times a year is usually fine.

I generally set the fade hight in UBL to 1mm. With a 0.1mm layer height, it applies full UBL correction to the first layer, 90% to the second, etc. At layer 11, the applied correction is zero, because the layers are theoretically perfectly flat at that point, at least as far as the kinematics of the printer are concerned.

Thank you very much for the explanation dude.
As I understood, I should look for leveling to make fine first layers and adjust the nozzle's height during the print to make the corrections.
Are there any other uses for 'the bed probing' besides the bed leveling procedure and using it as endstop? And the UBL saves the results in EEPROM?

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sajjsamm
Thank you very much for the explanation dude.
As I understood, I should look for leveling to make fine first layers and adjust the nozzle's height during the print to make the corrections.
Are there any other uses for 'the bed probing' besides the bed leveling procedure and using it as endstop? And the UBL saves the results in EEPROM?

Correct, although at least on my printer, with my nozzle detecting under-bed piezo probe, no Z height adjustment is required. Zero millimeters is exactly zero millimeters. If I slice a disc 380 millimeters in diameter and 0.005 millimeters thick and print it, I get a 350 millimeter disc of 0.005 millimeter thick film.

After running the step by step UBL, you need to save the mesh it creates in a memory slot (defaults to slot 0), turn ON UBL, save that in settings, and make sure that leveling is turned ON after HOMING (G28) in configuration.h. Otherwise, every time the printer homes, it will turn off bed leveling.

Alright, I shall try it on my printer setup after completing the chassis and installing the motors and head.